This application claims the benefit of German patent application DE19915529.1, filed Apr. 7, 1999, herein incorporated by reference.
The present invention relates to a device for winding conical cross-wound bobbins at a constant yarn delivery rate.
It is known in conjunction with open-end spinning machines that their winding devices can be provided with a controlled yarn accumulator for temporary storage of the yarn being wound during the winding of conical cross-wound bobbins. Such yarn accumulators serve the purpose of adapting the different yarn winding rates occurring in the area of the winding device during the winding of conical cross-wound bobbins to the constant yarn delivery rate of the spinning device. In the known devices, the cross-wound bobbin is held during the winding process in a pivotably mounted creel and is customarily driven by a friction roller via frictional surface contact. The winding rate of the cross-wound bobbin in the area of its driven diameter corresponds thereby to the constant yarn delivery rate of the spinning device. Thus, as a result of the conical shape of the bobbin, when the yarn is wound on the smaller diameter end of the cross-wound bobbin, the instantaneous yarn winding rate is below the set value of the yarn delivery rate and, likewise, when the yarn is wound on the larger diameter end of the cross-wound bobbin, the instantaneous yam winding rate is above the set value of the yarn delivery rate. Thus, to compensate, the excess yarn length delivered from the spinning device during the intervals when the yarn is being wound on the smaller end of the bobbin is temporarily stored at an intermediate location in a yarn accumulator. This intermediately stored yam length is given off by the yarn accumulator when the yam winding rate of the winding device in the direction of the larger diameter end of the cross-wound bobbin rises above the yam delivery rate of the spinning device.
Additionally, the ratio between the small bobbin diameter and the large bobbin diameter determines the yarn length to be fed by the controlled yarn accumulator per yarn guide stroke. Since the ratio of the small bobbin diameter to the large bobbin diameter changes with the continuing increase of the bobbin diameter as the winding operation progresses, the yarn length which the yarn accumulator receives and gives off must also be constantly adapted. In order to achieve this purpose, it is known to associate a control device with the yarn accumulator to appropriately adapt the accumulated yarn reserve of the yarn accumulator to the progress of the winding process.
Known yarn accumulators comprise a pivot lever which can be pivoted toward and away from the yarn travel path, therewith temporarily lengthening and shortening the overall length of the regular yarn travel path. Customarily, this pivot lever is moveably mounted about an axis of rotation and can be positioned by a drive.
European Patent Document EP 0,284,149 teaches a controllable yarn accumulator whose position determining the accumulated amount of yarn can be varied by an electrical drive. A control of the electrical drive takes place via a control device receiving its initial information from a yarn tension sensor. That is, when the yarn tension changes during the winding of the cross-wound bobbin, e.g., as a function of changes in the instantaneous yarn winding rate, the control device reacts with a corresponding control of the yarn accumulator.
Furthermore, German Patent Publication DE 18 14 928 A1 teaches a bobbin cross-winding device for producing conical bobbins in which the yarn guide and an additional means which scans the circumference of the cross-wound bobbin are mechanically coupled via a cam disk and a lever linkage to the yarn accumulator.
Finally, German Patent Publication DE 24 54 917 C2 teaches a method and a device for winding conical cross-wound bobbins in which the yarn accumulator is continuously controlled in proportion to the bobbin circumference of the cross-wound bobbin. In order to determine the instantaneous bobbin circumference of the cross-wound bobbin, the pivotably mounted creel is provided with a measuring element which detects the pivot position of the creel and controls the position of the yarn accumulator via a mechanical coupling element.
The known devices for winding conical cross-wound bobbins have the disadvantage that the control of the yarn accumulator is deficient either on account of the plurality of mechanical coupling elements or that, as in the case of European Patent Document EP 0,284,149, the yarn accumulator length determined by the yarn tension measurement is relatively imprecise.
It is accordingly an object of the present invention to overcome the above-described problems of the known controls for accumulators in conical bobbin winding devices and, more particularly, it is an object of the invention to provide an improved device for more precisely controlling the yarn accumulator in a simple manner.
Briefly summarized, the present invention addresses this objective by a device which makes possible an exact control of the yarn accumulator at all times by detecting the instantaneously driven diameter of the cross-wound bobbin by a first sensor device, detecting the instantaneous position and/or the direction of movement of the yarn guide by a second sensor device, and connecting the two sensor devices to a control device. The control device controls of the yarn accumulator by taking into consideration not only the actual yarn winding rate of the winding device but also the ratio at the same point in time between the large and the small diameter of the cross-wound bobbin. In this manner, the precisely required amount of yarn is constantly stored in an intermediate fashion so that, during the winding of the cross-wound bobbin, undesired changes in yarn tension can be avoided to a very great extent.
In this manner, the instantaneous winding state of the cross-wound bobbin can be directly detected by using the sensor devices of the invention. Both the position of the yarn guide, which reflects the instantaneous point at which the yarn is applied to the cross-wound bobbin, and the instantaneous diameter of the cross-wound bobbin provide in real time the essential information as to the operating condition of the winding device necessary to determine the precise yarn length to be fed to the bobbin. Accumulator errors can be reduced to a negligible minimum by such an arrangement. In addition, a plurality of mechanical coupling elements are eliminated, which results in a fundamentally simplified accumulator device which also requires, in particular, less space.
Precise reference can be made to the instantaneous diameter of the cross-wound bobbin at the point at which the yarn is being applied to the bobbin by means of algorithms, stored in the control device, for defining the control signal for the drive of the yarn accumulator. This results in a very exact control of the yam accumulator.
A known device operating with a Hall sensor mechanism device can be provided to detect the particular pivot angle of the bobbin creel and thereby can advantageously serve as the sensor device for determining the instantaneous diameter of the cross-wound bobbin. A mathematical determination is an alternative possibility for determining the instantaneous, driven diameter of the cross-wound bobbin. Such a mathematical calculation may be performed by detecting the speed of the cross-wound bobbin by a sensor arranged on the bobbin creel and using the detected bobbin speed in conjunction with the known speed and diameter of the friction drive roller for determining the driven diameter of the cross-wound bobbin.
In a preferred embodiment of the invention, the drive of the yarn accumulator is designed as a stepping motor. The stepping motor can be very precisely controlled via the control device so that the winding conditions which are continuously changing during the winding process (i.e., the precise point at which the yarn is applied to the bobbin, which constantly changes as a result of the traversing motion of the yam guide, and the diameter of the cross-wound bobbin, which constantly changes as the winding operation progresses) can be reacted to and the amount of yarn to be stored, which is dependent thereupon, can be adjusted to directly compensate in a simple manner.
The invention will be explained in greater detail in the following disclosure of exemplary embodiments with reference to the associated drawings.